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Topic: Pipe and Bolt Engine Mod-Up (Read 69147 times)

voted although I do agree yours should have been available to vote for Steve. It would be different if you tried to submit something you did prior to this but as its obvious you followed the same time period as us not a issue. However I will bow to your rule making as it may prevent arguments in the future

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Turns out this life c**p is just one big distraction from death but a good one. For the love of god dont give yourself time to think.https://myshedblog.wordpress.com/

Dwayne, I meant to thank you for your exhaust valve details. The really interesting thing about the long passage for both inlet and exhaust is that it works so well.

I've been thinkng about it a lot. If the pressure pulses travel at lets say the speed of sound (sorry about the units) or 1100 ft/sec, and let's say the tube between valve and piston is a foot, then you'd set up a standing wave at about 550 hz or 550 RPM (that includes time for inlet pulse and release pulse for each revolution).

So the question is, can it exceed that and also run at even harmonics? Is there a "hump" to get over at 1-1/2 wavelength? What is the speed of your engine in RPM? Does it act as if there's a regulator for RPM if the pressure is increased beyond a certain speed --- all kinds of interesting stuff.......

It would seem that a separation of valve and cylinder isn't particularly limiting for a steam engine. This is similar to what David Urwick talked about in Model Engineer (quite a ways back) re Stirling engines.

I've been thinking about this in relation to separating the valve and cylinder on uniflow engines -- since they seem to actually require clearance volume anyway. Moving the inlet valve body away from the head down to the crankshaft would allow reduction of mechanical linkages.

The guy who got this right way back at the turn of the previous century was HH Groves. That guy was an unrecognized genius -- he was buildng steam model airplanes with crankshaft mounted rotary disk valves and uniflow exhaust a hundred years ago. It's like Parsons -- everything coming together in one fell swoop.

I am ashamed to admit that your talking a bit above my head atm so I will explain the way it goes in my head and maybe you can draw some conclusions from my ramblings.The engine will work from around 5-10psi up to around 50-60psi at which point the valve leaks to such a degree that the air gets past the O ring and the piston gets a constant pressure, This would probably be solved with a better design of valve but time was pressing.

Anyway discounting the above the air is stopped at the valve until the cam starts to lift at which point the airway open to allow the air through the pipework into the bottom of the piston. The disadvantages of this is that the pipe as well as the bottom of the piston all has to be pressurised before any force is applied to the bottom of the piston. Not only that but the ports in the valve are by necessity small I started with 1mm ports but that was not giving enough of a kick to the flywheel to complete it around to the next valve opening so I then opened it up to 1.5mm which ran but only just, in the end it took 2mm to get it running at the stage it is now. I didnt want to risk going bigger to run it faster as the limited movement of the valve may have caused a problem with it not closing properly. So as you may gather the 2mm hole has to supply air to a 5mm pipe and a 10mm piston a bigger port would of course allow the pressure to build much more quickly and the whole thing would go much faster.

The second disadvantage is that when the cam drops all the pressure is released and so all the air in the pipe is wasted having served no purpose.Hope this helps.

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Turns out this life c**p is just one big distraction from death but a good one. For the love of god dont give yourself time to think.https://myshedblog.wordpress.com/

The disadvantages of this is that the pipe as well as the bottom of the piston all has to be pressurised before any force is applied to the bottom of the piston.

Thanks Dwayne. This is the part I was thinking about, The amount of time it takes to travel must be very short, though, relative to the speed of the engine.

The long tube allows the engine to run a lot better than I would have thought, just looking at it intuitively. What really surprised me was that you used the same valve body for exhaust, which meant the long tube had to serve double duty. And yet the engine still ran at respectable speed.

The clue to why it works so well, I think, is that the pressure pulses from the valve are traveling at the speed of sound down the tube and back.

If you have a foot of tube, and sound travels at about 1100 feet per second, it would mean that piston starts to feel pressure a little less than 1 milisecond after the valve starts to open. That's the interesting part.

As said by others, I wanna vote for both as both are unique takes on the broad brush stroke challenge. Interesting too, that after I submitted my vote I saw the progress score and with only 13 votes logged I shall wait patiently to see how the votes tally later. BIG congrats to both of you.

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Converting good metal into swarf sometimes ending up with something useful. ;-)

I followed this thread clear through and was/am very impressed. I voted only to register that I was interested in all the designs. My choice was hard but the rotary type of valve intrigued me enough to possibly try to incorporate it into some future model I may make. My models do not compare to most of the fine machining on this site but I enjoy reading the posts each day---Thank You for the fine site and many hours of entertainment.

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Hammer to shape, shim to fit and paint all over.A little bit of paint covers a multitude of sins.

Congratulations Russell, the valve was the coolest thing I've seen in small steam engines in a long time -- that's pretty hard to top! And nicely executed and videod -- with the breath demonstration and also the reversing capability. Just all around impressive, A well deserved trophy for that!

And Dwayne, that is a very fine strictly pipe, bolt (and nail) engine, that I've learned a lot from. The large valve tube clearance volume still intrigues me, and I will have more to say about that in future, because I think it's important to performance and construction techniques for some kinds of engines.

Also the valve mechanism is really fun to watch and listen to. In fact I've gone so far as to put it through an audio analyzer, and so I can tell you that your engine was running in the video at 261 RPM, in case you're curious! Thank you for allowing us all to enjoy your build,..... and I'm still envious of your true bent pipe flywheel. I wish I could bend a circle like that in pipe.

Thanks also to readers too for encouraging these two, and I hope Madmodders will think up more group builds and contests for this new Mod-up section. It's your forum for your ideas in how to have fun with joint projects.

Also the valve mechanism is really fun to watch and listen to. In fact I've gone so far as to put it through an audio analyzer, and so I can tell you that your engine was running in the video at 261 RPM

Well That saves me a job I was going to tape a magnet to it this weekend and use a coil with my multimeter to figure out the rpm as I dont have a proper tacho, although I may still do it. The video had the engine running with around 20 psi I believe, I would like to see the maximum speed with ports as they are then try to open them up a little and see the difference

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Turns out this life c**p is just one big distraction from death but a good one. For the love of god dont give yourself time to think.https://myshedblog.wordpress.com/

...Thanks also to readers too for encouraging these two, and I hope Madmodders will think up more group builds and contests for this new Mod-up section. It's your forum for your ideas in how to have fun with joint projects.

Agreed!

Not just engine builds either. Anything and everything is fair game for these builds. Want to do something with LEDs? Carbon Fiber? Have at it!

I feel like I've just won an Oscar and now have to make a gracious acceptance speech.

I'd like to thank all the contributors to this thread for their encouragement, kind words and most importantly motivating me to have a go. I am especially pleased with the positive comments from those members who have more experience in these areas than me and whose views I respect.

The only slight disappointment is that more people didn't have a go. I was a bit worried about posting my progess on an unproven idea in case it didn't work, but I'm glad I did. I enjoyed the whole build and reporting.

You should all have a go at the next one. I'm sure you'll enjoy it and learn something from it.

Congratulations Russell,you did a fine job on this Mod up challenge. It was your clever valve mechanism that swayed it for me.

Great effort Dwayne, your engine is also a cracker,and as others have said the rolled flywheel was really well executed.

If I had to choose an engine for looks then it would have to be Steve's as it looks very much like a model of an agricultural stationary engine and in that grey and red colour scheme it reminded me of the old Fergusson tractors. For looks it appeals very agreeably with my taste in engine design......OZ.